It is known that the electrical resistance of a conductor within a defined temperature range can be varied over broad limits. At low temperatures the resistance of a metal such as pure bismuth or tungsten can be varied in a ratio of 1:100,000 by means of changes in a magnetic field surrounding the conductor.
It is also known that the resistivity of many conductors will decrease to zero as the temperature approaches absolute zero, i.e., a state of superconductivity is evident.
The change of resistance in a superconductor is dependent on changes of magnetic field and temperature in accordance with the following expression: ##EQU1## which shows the dependence of the resistance R on changes of the field strength H at constant temperature, and on changes in the temperature at constant field strength H.
J. Math. Phys., 25(11), 2325(1984) by A. C. Eringen proposes a general nonlocal continuum theory which is applied to superconductivity, and which treats Maxwell's theory of electromagnetism as a special case.
Another critical factor which affects the resistivity of a conducting medium is the physicochemical structure of the matrix. Thus, heavy doping of a semiconductor such as gallium arsenide can yield a medium which is superconducting at temperatures approaching zero degree Kelvin.
Recent events have focused attention on the superconducting species of the copper oxide perovskit family of crystalline compounds. Interest was initiated with the discovery of superconductivity above 30 K by J. G. Bednorz and K. A. Mueller in La.sub.2-x Ba.sub.x CuO.sub.4-y, as reported in Z. Phys., B64, 189 (1986).
The prospect of a room temperature superconductor has stimulated a broad scope of investigational activities in many academic and corporate laboratories. Physical Review Letters and the Japanese Journal of Applied Physics and other publications have begun to report new advances in superconductivity, such as the 90 K series of compositions based on YBa.sub.2 Cu.sub.3 O.sub.x and the yttrium-lanthanide substitutions.
There is intense interest in the development of new and improved electrical conductors having exceptional properties, and in processes for their preparation.
Accordingly, it is an object of this invention to provide a process for the preparation of electrical conductors with decreased resistivity.
It is another object of this invention to provide a process for raising the critical temperature T.sub.c level of a superconducting medium.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.